1. Field of the Invention
The present invention relates to an image file format for storing graphical matter and related information for use in producing graphics output, such as print output.
2. Description of the Related Art
In publishing, the pages of a document are scanned, transformed into a printer readable format, and then printed and/or archived in a computer storage device for subsequent retrieval and printing. Publishing software is used by publishing companies to electronically print and archive books. Pages of a document are scanned to produce an electronic bit-map representation of the pixels on the scanned page and the pixel color values. The page may contain line art, e.g., text and lines, and/or continuous tone, e.g., images. For black and white images, the scanned image is stored as a grey scale image wherein each pixel represented on the bit map has a corresponding shade of grey value. Optical scanners typically allow for anywhere from 16 to 256 shades of grey for each pixel. A bit map of a page that allows for grey scale values requires 4 to 8 bits for each pixel to indicate the different shades of grey. A bit map representing text only, where the pixel is either black, i.e., xe2x80x9con,xe2x80x9d or white, i.e., xe2x80x9coff,xe2x80x9d only requires 1 bit per pixel to indicate either xe2x80x9conxe2x80x9d orxe2x80x9coff,xe2x80x9d black or white. A bit map that represents a color page, including line art and continuous tone, requires even more space than black and white images. Each pixel of a scanned color image can be one of 16.7 million colors, which requires 24 bits for each pixel.
After the page is scanned, the bit map produced by the scanner must be further processed into a bit map format that the printer can process. The transformation of the scanned bit map into a printer readable format is referred to as halftoning or raster image processing (RIP). In a publishing environment, halftoning or transforming, i.e., RIPping, numerous bit maps that represent the pages of a large document, such as a book, can take several hours. The result of the halftone transformation is a bi-level image, where each bit map value indicates either black or white. The halftoning transformation would use dithering to produce a wide level of shades of grey or colors. Dithering refers to the illusion of printing colors or shades of grey by varying the patterns of dots. Thus, a bit map where each bit map value can correspond to one of many values indicating different shades of grey or colors is converted to a bi-level bit map where each value indicates one of two colorsxe2x80x94black or white. However, the halftoning or transformation process uses dithering to simulate the shades of grey or different colors. The term xe2x80x9cgray scalexe2x80x9d as used herein refers to a bit map where each bit map value can be one of numerous values, indicating different colors or shades of grey. The term xe2x80x9chalftonexe2x80x9d as used herein will refer to the transformed grey scale bit map to a bit map that can be processed by the printer. A halftone bitmap may be a bi-level bit map where there is only one value for each pixel, i.e., 0 or 1. Contone printers print a limited number of shades of a color or grey. Thus, a halftone bit map for a contone printer may include a limited number of values for each bit map value and also use dithering to simulate additional shades of grey and color. The term xe2x80x9chalftoningxe2x80x9d as used herein refers to the transform process of transforming a gray scale bit map to a printer readable format, such as a bi-level bit map or contone bit map capable of a limited number of different values for each pixel that are available on the printer. Halftone bit maps are typically specific to a particular printer, i.e., device dependent.
The gray scale or halftoned bit map of each page in the book may be stored in one or more files. For instance, the tagged image file format (TIFF(trademark))** stores one bit map for each page in a single file. A TIFF file can store both the gray scale bit map and a halftoned bitmap.
The gray scale bit map is referred to as device independent because it represents the image without reference to a specific device. The halftone bit map is device dependent as the gray scale bit map was transformed to halftone bit map that is particularly suited to the dithering capabilities of the printer on which the halftone bit map will be printed.
Some publishers will archive the halftone bit maps of every page in a book. This method uses less space than storing the gray scale bit maps for each page and does not require subsequent transformation processes, e.g., RIPping or halftoning, when the archive file is later retrieved to reprint the book or document. However, the halftone bit map is device specific and reproductions of any images from the halftone bit map on printers different from the printer for which the transform was made will be poor quality. Further, reprinting the halftone image on the same printer at different times may produce low quality. To produce high quality images, some publishers may maintain a record of all pages in the book or document that contain continuous tone images. Using this record, the publisher will then re-scan those pages including continuous tone images and then RIP or halftone the rescanned pages for printing. This process requires substantial manual labor to access and re-scan the pages including continuous tone in the book or document.
An alternative method used today in publishing is to archive the gray scale bitmaps for each page in the book or document. This method provides a device independent bit map which may be utilized on different printers. Nevertheless, this method is problematic for at least two reasons. First, this process is very costly in processor cycles as the gray scale bit map for each page must be transformed into the halftone bit map. Performing numerous of these transforms will substantially degrade printer performance. Second, is that gray scale bitmaps require substantially more, storage space than a halftoned or bi-level bitmap. For instance, a page represented as a gray scale bit map can consume 32 megabytes (Mb) of storage, whereas a page represented as a halftoned or bi-level bit map only requires 4 Mb of storage. Moreover, compression algorithms on gray scaled pages that include both text and continuous tone image do not perform well. A lossless or LZW algorithm will substantially compress the text but only minimally compress the continuous tone image. Compression algorithms that are effective at compressing text, such as lossy and JPEG, will degrade the quality of the text component of the bit map. The printed text will be blurred at the edges as a result of such image oriented compression algorithms.
There is thus a need in the art for an improved method of archiving bit mapped representations of documents including both line art and continuous tone images.
To overcome the limitations in the prior art described above, preferred embodiments disclose a system, method, program, and data structure for processing graphics input. The graphics input may include a first and second types of graphics matter. At least two data structures including representations of a same graphics matter are provided. An object is generated to include information on the data structures, including information relating the data structures. The object is then processed to produce graphics output including the graphics matter in the graphics input.
In further embodiments, the graphics input includes the first and second types of graphics matter. In such case, the data structures may be provided by transforming a data structure in a first format representing the graphics input to a data structure in a second format representing the graphics, input. A determination is then made as to the second type of graphics matter in the graphics input. At least one data structure in the first format representing the determined second type of graphics matter is generated. In such case, the information in the generated object comprises information on the transformed data structure in the second format and each generated data structure in the first format. The information further relates each generated data structure with the transformed data structure. The related generated and transformed data structures each include representations of a same graphics matter of the second type.
The first format may be a device independent data structure and the second format is a device dependent format. For instance, the first format may be a gray scale bit map having values indicating either colors or shades of grey and the second format may be a bi-level bit map.
In further embodiments, the object may comprise a TIFF file and the information on the transformed data structure and generated data structure are maintained in image file directories (IFDs).
Preferred embodiments provide an image file format in which both device dependent data, such as the halftone of a page, and device independent data, such as the gray scale of the continuous tone images in a page, are maintained. This allows the image file format to provide sufficient information to generate high or low quality output for a print job and at the same time minimize use of storage and processor resources. If the user wants to print a proof at a low quality, then the device dependent data, i.e., already transformed bit map, will be used to generate print output. This will maximize printing performance and minimize use of processor cycles. However, if a high quality print job is desired, then those parts of the print job, such as the images, will be generated by transforming the device independent data also maintained in the image file format. Although this requires further processing time and reduces printing performance, processing time is minimized because only those portions of the print job having continuous tone are generated from the device independent data. For those pages including only text or line art, the device dependent data is sent to the printer without having to perform the costly transformation processes. The device dependent data is usually sufficient to produce high quality output for line art or text. Thus, use of processor cycles to transform device independent data, such as gray scales, is minimized by transforming only those portions of the print job that need to be transformed or halftoned again to produce high quality print output. This in turn minimizes degradation of printer performance while maintaining enough printer image information to produce high quality output.
Preferred embodiments further conserve storage resources. Typically, the device dependent bit maps use significantly less storage space than device independent bit maps. With the preferred file format, device independent bit maps are only maintained for those parts of the print job that need to be transformed at printing time to produce high quality. This insures that high quality can be maintained and minimizes storage resources because device independent data is only maintained for those parts of the print job that require transformation or halftoning of the device independent data in order to produce the desired high quality.